[Non-BE] Resolve "MSAN: use-of-uninitialized-value in Planar OSBA to STEREO decoding"

• Related issues: #1014 (closed), #1015 (closed), #1016 (closed)
• Requested reviewers: @weckbecker

Reason why this change is needed

The discrete ISM rendering does not update the subframe information in the TC buffer as needed.

Description of the change

Update the subframe information in the correct way, i.e. for all cases apart from a following call to CREND.

Affected operating points

• Non-BE since it fixes at least one decoder crash.
• Produced bitstream is BE compared to previous state (no encoder change).

Related to #1014 (closed)